2. People with mild dementia associated with PD, where the patient and/or their family have become aware of cognitive with or without behavioural symptoms that are causing functional impairment. "Dementia" will be defined according to recently published Movement Disorder Society Task Force criteria for dementia associated with Parkinson's Disease and "operationalised" using the Addenbrooke's Cognitive Examination (ACE-R). The ACE-R permits some description of the dementia profile and also quantifies global impairment. It is increasingly used by clinicians in the UK to identify demented subjects, is relatively quick to perform (15 minutes or so), requires no specific training and produces a total score (0-100), from which the MMSE (0-30) can also be extracted. Participants will have an ACE-R of 88 or less. If this criterion is met, subjects will be further assessed using the Mattis Dementia Rating Scale (DRS-2). An age- and education-corrected total DRS-2 score of less than 8 but greater than 4 (corresponding to between the 6th and 28th percentile) will be used to define "mild" dementia".